Editing Cerebral arteriovenous malformation (section)

==Pathophysiology==
A cerebral AVM is an abnormal [[anastomosis]] (connection) between the [[arteries]] and [[vein]]s in the [[human brain|brain]] due to the lack of a [[capillary bed]], and is most commonly of [[prenatal]] origin.<ref name="Mayo-Causes">{{Cite web|url=http://www.mayoclinic.com/health/brain-avm/DS01126/DSECTION=causes |title=Brain AVM (arteriovenous malformation)-Causes |author=Mayo Clinic staff |date=February 2009|publisher=Mayo Clinic |access-date=2010-05-30}}</ref><ref name="Mouchtouris"/>

In normal [[cerebral circulation]], [[oxygenated blood|oxygen-enriched blood]] from the [[heart]] travels in sequence through smaller blood vessels going from arteries, to [[arteriole]]s and then [[capillaries]].<ref name="Mayo-Causes"/> Oxygen is removed in the capillaries to be used by the brain.<ref name="Mayo-Causes"/> After the oxygen is removed, blood reaches [[venules]] and later veins which will take it back to the heart and [[lung]]s.<ref name="Mayo-Causes"/> A cerebral AVM causes blood to be shunted directly from arteries to veins because the capillary bed is lacking, causing a disrupted [[Circulatory system|circulation]].<ref name="Mayo-Causes"/><ref name="Mouchtouris">{{cite journal|last1=Mouchtouris|first1=Nikolaos|last2=Jabbour|first2=Pascal M|last3=Starke|first3=Robert M|last4=Hasan|first4=David M|last5=Zanaty|first5=Mario|last6=Theofanis|first6=Thana|last7=Ding|first7=Dale|last8=Tjoumakaris|first8=Stavropoula I|last9=Dumont|first9=Aaron S|last10=Ghobrial|first10=George M|last11=Kung|first11=David|last12=Rosenwasser|first12=Robert H|last13=Chalouhi|first13=Nohra|title=Biology of cerebral arteriovenous malformations with a focus on inflammation|journal=Journal of Cerebral Blood Flow & Metabolism|date=19 November 2014|volume=35|issue=2|pages=167–175|doi=10.1038/jcbfm.2014.179|pmid=25407267|pmc=4426734}}</ref>

The overall annual incidence of [[haemorrhage]] from a ruptured AVM is 2-4%. Smaller AVMs have a greater propensity for haemorrhaging, whereas larger AVMs tend to more often cause seizures instead.<ref name=":02">{{Cite book |title=Schwartz's Principles of Surgery |edition=11th |publication-date=2019 |pages=1853}}</ref>